Disposable, breath-actuated inhalers are known in the prior art. In most of the known inhalers the powder to be inhaled is loosely provided in the inhalation channel as can be seen in for example in EP-A-0 404 454 and U.S. Pat. No. 4,265,236.
In the known above-mentioned devices the powder is provided loosely in a relative large chamber which functions as powder compartment and inhalation channel being provided with air inlet and outlet. The powder in the inhalation devices of the above-mentioned type has a particle size which is generally smaller than 10 .mu.m whereby strong cohesive forces are present between the powder particles. These cohesive forces causes the creation of aggregates of powder which are created during handling and storage of the inhaler. When the powder is freely movable within a chamber as in the above mentioned documents an uncontrolled creation of aggregates will occur. These aggregates could either be to big to be inhaled or too big to enter into the bronchial region of the patient, e.g. larger than 10 .mu.m. With the powder freely movable within a chamber the powder will also stick to the walls due to the adhesive forces between the particles and the walls as well as to electrostatic forces occurring in the device.
These drawbacks are solved in the inhalation devices as described in WO 92/04069 and WO 93/17728. In the constructions according to these applications the powder is provided in a compartment which is provided as an indent or cavity in the lower part of the housing of the inhaler. The powder compartment, the cavity, is provided close to the air inlet, and the air flow path is provided with a constriction adjacent the powder compartment in order to create an acceleration of the air flow to lift the powder dose out of the cavity and mix it with the inhalation air flow during inhalation. In WO 93/17728 a hole is provided in the cavity in order to facilitate the lifting of the dose into the inhalation air flow. In order to break down the aggregates of the powder dose into respirable particles the inhalers as described in these two applications are provided with deaggregation means provided within the air flow path.
The cavity and thereby the powder dose is protected before inhalation by two tapes, one covering the upper opening of the cavity and the other covering the hole in the lower part of the cavity thereby providing a moisture proof device.
However, the construction of the known devices is provided with several disadvantages.
The inhalers according to the above mentioned applications are constructed with a housing having an upper and a lower part sealed to each other wherein the two parts are made of different materials. The upper part is made of plastic material whereas the lower part in which the powder compartment or cavity is placed is made of aluminium or a laminate of aluminium and plastics. Furthermore, the cavity and thereby the hole in the cavity are provided in an unprotected manner and the cavity can easily be damaged during handling and storage of the inhalers. Moreover, as the hole is provided in the lower part of the cavity it is easily covered by a user's thumb or hand during inhalation whereby the function of the inhaler is jeopardised as the dose or parts of the dose may not be properly lifted out of the cavity.
These disadvantages are solved by the inhalation device according to the present invention.
The present invention provides a disposable breath-actuated dry-powder inhalation device of the above mentioned kind wherein the disadvantages of the known devices are eliminated.
The present invention also provides a construction which is more stable and rigid than the prior devices. It is also cheap and easy to produce and uses as little aluminium or laminates of aluminium as possible in order to minimise the stress to the environment
The inhalation device according to the invention could be manufactured in a transparent material in order to make it possible for the patient to inspect the inhalation device and the dose before and after inhalation.
The above objects of the present invention are achieved by the features set out in claim 1, whereby the powder compartment is formed as a cavity or indent in a plate and placed in the housing in the air flow path.
In the present inhalation device the hole in the powder compartment/cavity is protected and can not be damaged during handling and storage and/or be covered during inhalation.
Further advantages and objects are clear from the features as set forth in the appended claims.